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Aug. 5, 2011 -- A little bit of weight loss may revive the sex lives and improve the urinary health of men who are obese and have diabetes, a new study shows.

Obesity and diabetes can take a toll on the penis and urinary system, which are sensitive to changes in blood flow, inflammation, and hormone levels.

“Everything that makes your blood vessels bad is also bad for erectile function,” says Ronald Tamler, MD, PhD, clinical director of the diabetes center at the Mount Sinai School of Medicine in New York. “The small arteries around the penis go down the drain first.”

Symptoms often include difficulty getting or keeping an erection, low libido, infertility, and problems with urination, including the need for frequent, sleep-stealing trips to the bathroom in the middle of the night.

Previous studies have shown that dropping a large amount of weight, about 30% of total body weight, a feat typically achieved through weight loss surgery, can improve many of those problems.

The new study is one of the first to show that smaller losses -- 5% to 10% of total body weight or about 11 to 22 pounds for a 220-pound, 6-foot-tall man -- may bring about the same degree of improvement.

“Within a very short space of time, with a very modest amount of weight loss, there was quite a marked improvement in erectile function,” says study researcher Gary A. Wittert, MD, a professor who is also head of the department of medicine at the University of Adelaide in Australia.

“Some of the men, who were quite significantly impaired, improved quite markedly and continued to do so up to a year later,” Wittert tells WebMD.

Experts said although the study was small, with just 31 participants, it was noteworthy because it followed the men for a long time and carefully measured changes in symptoms and biomarkers like hormones.

“This is the type of study that we need,” says Drogo Montague, MD, director of the Center for Genitourinary Reconstruction at the Cleveland Clinic in Ohio, who was not involved in the research.

“It’s definitely an underappreciated problem,” Montague says. “We have an epidemic of obesity in our society and we’re seeing this more and more and more. I’ve seen patients who have had dramatic reversal of loss of libido and poor erections through weight loss.”

“This is kind of a way of showing that even smaller amounts of weight loss can be effective, and it’s done it in a more scientific way,” he says.

Weight Loss to Improve Sexual Health

For the study, researchers recruited obese men who had body mass indexes (BMIs), a number calculated from weight and height, of greater than 30 and waist sizes over 40 inches. A large waist is an indication of having a lot of fat stored around the belly.

The average age of men in the study was 60. Study participants had an average BMI of 35, and the average length of time they had been diagnosed with diabetes was four to five years.

More than half the men in the study reported having symptoms of severe erectile dysfunction, and about one in three said they had at least moderately severe lower urinary tract symptoms (LUTS), including problems with frequency, urgency, weak stream, and incontinence.

The men were randomly assigned to either a low-calorie diet, where two daily meals were replaced by weight loss shakes, or to a higher-protein, lower-carbohydrate eating plan.

In the meal replacement plan, men got about 900 calories a day.

In the healthy eating plan, which focused on three meals of lean protein, five daily servings of vegetables, and two daily servings of whole grain carbohydrates and fruit, was designed to shave about 600 daily calories off what the men would normally eat. “We’re talking fresh lean meat, chicken, and fish,” Wittert says. “We’re not talking about processed meats, we’re not taking about fatty meats or very large portions.”

After eight weeks, the men on the low-calorie meal replacement diets were switched to the healthy eating plan, and all continued to be followed for a year.

Small Changes, Big Benefits

After eight weeks on the diets, the men on the low-calorie plan had lost about twice as much weight as the men on the healthy eating plan, 20 pounds vs. 11 pounds.

But they had similar improvements in erectile function, sexual desire, and urinary symptoms.

Wittert thinks the group on the healthy eating plan saw as much improvement as the low-calorie diet group, in part because they were getting more needed vitamins and minerals and phytochemicals.

“Part of the effect was related to weight loss but part of the effect is also, I think, related to the nutritional quality of the diet,” he says.

Many obese people, Wittert thinks, are, ironically, undernourished.

“You can eat large amounts of calories but not get adequate nutrients,” he says.

Of the 17 men with severe erectile dysfunction, Wittert says that after eight weeks, seven had improvements in their symptoms, with some achieving normal function. After a year, 25% had normal erectile function.

Similarly, urinary symptoms decreased significantly in both groups at eight weeks and continued to improve in the year that the men continued on the healthy eating plan. The more weight the men lost, the greater the improvements.

They also had better blood flow, improvements in markers of inflammation, and saw increases in testosterone, which is necessary for the production of healthy sperm and plays a role in sex drive and sexual performance.

“Fat tissue constantly makes inflammatory products,” Tamler says. “People who are obese have more inflammation going on in their body, and inflammation suppresses testosterone production.”

Tamler says fatty tissue also makes an enzyme that may change the male hormone testosterone to the female hormone estradiol. “The more fat you have, the more conversion you get,” he says.

“As these men lose weight, they have less inflammation, less conversion, and more testosterone,” says Tamler, who has studied the effects of weight loss on erectile function, but was not involved in the current research.

The study is published in the Journal of Sexual Medicine.

Advice to Men

Researchers say the diet they used is easy to copy at home and adding physical activity may result in even bigger benefits.

“There’s no question that physical activity has a benefit in and of itself,” Wittert says. “I often tell the guys that I look after, ‘Come home in the evening and instead of sitting in front of the television with a bag of chips and a beer, take your wife by the hand and say, ‘Come darling, let’s go for a walk.’”

He says that after doing that for a few weeks, “her heart will grow fonder, and your erection will be longer and stronger.”